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module math
import math.internal
fn poly_n_eval(c []f64, n int, x f64) f64 {
if c.len == 0 {
panic('coeficients can not be empty')
}
len := int(min(c.len, n))
mut ans := c[len - 1]
for e in c[..len - 1] {
ans = e + x * ans
}
return ans
}
fn poly_n_1_eval(c []f64, n int, x f64) f64 {
if c.len == 0 {
panic('coeficients can not be empty')
}
len := int(min(c.len, n)) - 1
mut ans := c[len - 1]
for e in c[..len - 1] {
ans = e + x * ans
}
return ans
}
[inline]
fn poly_eval(c []f64, x f64) f64 {
return poly_n_eval(c, c.len, x)
}
[inline]
fn poly_1_eval(c []f64, x f64) f64 {
return poly_n_1_eval(c, c.len, x)
}
// data for a Chebyshev series over a given interval
struct ChebSeries {
pub:
c []f64 // coefficients
order int // order of expansion
a f64 // lower interval point
b f64 // upper interval point
}
fn (cs ChebSeries) eval_e(x f64) (f64, f64) {
mut d := 0.0
mut dd := 0.0
y := (2.0 * x - cs.a - cs.b) / (cs.b - cs.a)
y2 := 2.0 * y
mut e_ := 0.0
mut temp := 0.0
for j := cs.order; j >= 1; j-- {
temp = d
d = y2 * d - dd + cs.c[j]
e_ += abs(y2 * temp) + abs(dd) + abs(cs.c[j])
dd = temp
}
temp = d
d = y * d - dd + 0.5 * cs.c[0]
e_ += abs(y * temp) + abs(dd) + 0.5 * abs(cs.c[0])
return d, f64(internal.f64_epsilon) * e_ + abs(cs.c[cs.order])
}
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